1. Field Of The Invention
2. Description of Related Art
Coiled tubing (xe2x80x9cCTxe2x80x9d) is typically relatively long continuous lengths of pipe, known as strings, which can be run in and out of a bore, pipeline, tubular string, borehole, or wellbore. The CT is usually made of steel or steel alloy, though it may be made of plastic, composites, titanium or other materials. The CT is typically stored on a reel.
CT strings typically have a constant outside diameter (OD). Its OD designates the CT size. Some typical CT sizes are 1.0xe2x80x3, 1.25xe2x80x3, 1.5xe2x80x3, 1.75xe2x80x3, 2.0xe2x80x3, 2xe2x85x9cxe2x80x3, 2⅝xe2x80x3, 2xe2x85x9exe2x80x3 and 3.5xe2x80x3. The wall thickness of the string may be constant, or may vary along the length of the string. Strings with varying wall thickness along the length of the string are known as xe2x80x9ctaperedxe2x80x9d strings. U.S. Pat. No. 4,629,218 describes tapered strings. U.S. Pat. Nos. 4,863,091 and 5,191,911 describes manufacturing processes used for some conventional steel CT strings.
Some prior art stepped outer diameter (xe2x80x9cODxe2x80x9d) CT strings are made by connecting sections of CT with different outer diameters. A section of pipe with a machined OD varying from one size to the next is used in making the transition connection between one size and the next. For example, a stepped OD string may be made by connecting 5,000 ft. of 1.5xe2x80x3 CT to 5,000 ft. of 1.75xe2x80x3 CT. Another 5,000 ft. of 2.0xe2x80x3 CT is connected to the 1.75xe2x80x3 forming a 15,000 ft. string made of three sizes of CT. Use of some of these prior art stepped OD strings has been limited due primarily to concerns about the bending fatigue life of the string at connections.
Certain prior art manufacturing processes for steel CT include three steps or processes. In the first process, rolls of sheet steel known as master coils, typically 4 ft. to 6 ft. wide and 1,000 to 3,500 ft. long, are slit and into strips which are rolled into slit coils (e.g. like the coils 100 in FIG. 1). The strips in these slit coils are the length of the original master coil and are the width necessary to make the particular CT size being manufactured. The thickness of these strips may be constant or may vary gradually along the strip length to form a continuous taper as is described in U.S. Pat. No. 4,629,218.
In the second process, shown in FIG. 1, strips from the slit coils 100 are welded together at the welder 101, typically using biased welds described in U.S. Pat. Nos. 4,863,091 and 5,191,911. Once the weld is completed and inspected, the strip is spooled onto a large strip reel. Successive strips may have the same thickness as the previous strip, or may have a different thickness. If the strip thickness differs, the final CT will be a tapered string. As multiple strips are welded together, one long continuous strip is made on the strip reel to the desired length of the CT string, typically between 7,000 and 25,000 ft. long.
In the third process, shown in FIG. 2, the strip 103 from the large strip reel 102 passes through a series of sub-processes which manufacture or mill the strip into CT. In the first sub-process 104 the strip 103 passes through forming rollers that form the strip into a tube shape 105. These forming rollers are powered so that they pull the strip from the large strip reel 103 and move it through the milling process. In the next sub-process 106 the edges of the tube are welded together to form a longitudinal seam weld, typically using an electric resistance weld (xe2x80x9cERWxe2x80x9d) though other weld types may be used. When an ERW process is used an impeder is often placed inside the tube at the point where the weld is being created. As part of this welding process 106 a cutter cuts away the external weld flash. There may also abe an internal cutter that cuts away the internal weld flash. In the next sub-process 108 the weld seam of the welded tube 107 is heated to a temperature that normalizes the grain structure of the material. As part of the seam normalizing process 108 the seam is cooled by passing for a period of time through the air. In the next sub-process the tube 109 passes through sizing rollers that reduce the tube diameter slightly to its final size. These sizing rollers are also powered and help the forming rollers in moving the tube through the milling process. The sized tube 111 then passes through the next sub-process 112 in which it is heated to a stress relief temperature and then allowed to air cool. After air cooling the tube passes through a water bath for the final cooling 114. The completed tube 115 is then spooled onto a CT reel 116.
In certain embodiments, the present invention provides coiled tubing strings in which the outer diameter varies continuously or nearly continuously over a portion of the string""s length. Methods according to the present invention for making such strings are also disclosed. These continuously varied OD CT (xe2x80x9cVODCTxe2x80x9d) strings can be designed for excellent performance in many situations. In certain aspects they reduce or eliminate bending fatigue problems associated with prior art stepped OD CT strings.
In certain embodiments VODCT strings according to the present invention provide additional strength where it is needed; modify the velocity and pressure profile in a CT string and/or in the annulus between the CT string and the bore; provide the larger diameter where needed while meeting weight and size restrictions; have varying wall thickness; and/or provide diameter profile needed when snubbing against high pressures.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention.
The present invention recognizes and addresses the previously-mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one skilled in this art who has the benefits of this invention""s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent""s object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.
What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain preferred embodiments of the invention, other objects and purposes will be readily apparent to one of skill in this art who has the benefit of this invention""s teachings and disclosures. It is, therefore, an object of at least certain preferred embodiments of the present invention to provide:
New, useful, unique, efficient, nonobvious coiled tubing strings or parts thereof with an outer diameter that varies continuously or nearly continuously over all or over a portion of the strings"" length;
Methods for making such CT strings;
Such strings that can modify velocity and pressure profiles in a CT string; and
Such strings that provide larger outer diameter in a desired location and/or provide a diameter profile needed when snubbing against high pressure.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention.